Flashing lights are used as additional approach and threshold identification lights at airports in poor weather conditions, when the effect of the normal approach lighting is not sufficient to guarantee good, visual approach guidance. However, it may also be expedient to additionally use flashing lights in good visibility conditions, for example in order to make it easier to find the runway in urban areas.
Flashing lights are used in precision approach lighting systems as a threshold flashing system or as a combined approach flashing and threshold flashing system, whose functionalities and characteristics are described in the International Civil Aviation Organization (ICAO) Standard, Annex 14, volume I, part 1, paragraph 5.3.4, and in the Federal Aviation Administration (FAA) Standard, AC5345-51, E-2628b. Flashing lights may be in the form of surface-mounted lights for one emission direction, in the form of surface mounted omnidirectional lights, or else in the form of flush-mounted lights for one emission direction.
The DCF-1-120 flush-mounted flashing light is known from the German product specification “Blitzfeuer mit Vorschaltgerät für Anflug und Schwelle” [Flashing light with a ballast for approach and threshold], issued in 1999 by Siemens AG, with the Order No. E10001-T95-A65-V1. Each flush-mounted flashing light has an associated ballast which contains the components for supplying and igniting a 2000 V DC voltage flash tube. The flash energy is stored in capacitors. A coded counter, which is located in each ballast for the known flashing light system and is synchronized by the timer in a master ballast, determines the subsequent pulse which ignites the lamps, and in response to which the capacitor discharges its energy as a light flash. Each flashing light system has an associated system control cabinet as an interface for control and monitoring of the flashing system. A six-core special cable is used for the electrical connection between the flush-mounted flashing light and the ballast and its length may be up to 30 m. The system control cabinet is used to drive the ballasts either remotely or in situ with one or with three brightness levels.
This known DCF-1-120 flush-mounted flashing light has a multiple part housing, which comprises a cylindrical housing pot which is closed from underneath by a housing base composed of cast aluminum alloy, and whose upper face is covered by an upper part which is in the form of a plate and surrounded concentrically by an outer ring, composed of cast steel. An optics assembly is arranged in the housing pot and has a xenon discharge lamp as the light source for production of light flashes, as well as lamp holders, rubber grommets, an ignition transformer, a locking switch and a terminal block. The aluminum highly-reflective mirror is used to guide the light produced by the discharge lamp in the direction of a prism, which is adhesively bonded in the housing upper part. The prism changes the direction of the beam direction of the light flashes, so that they leave the flashing light in a predetermined emission direction through light outlet openings in the housing upper part. The emission angle is horizontally (in azimuth) between +15° and −15° and vertically (in elevation) between +2° and +12°. The effective minimum light intensity of 150 Cd, 500 Cd or 5000 Cd is produced by light flashes with an energy of 60 J per flash, at a maximum power of 120 W. With an emission rate of two flashes per second produced by discharging a capacitor which is charged to 2000 V, a 100 mm long xenon gas-discharge tube is required to produce the power. Cadmium-plated steel is used for the large housing parts, while the small parts are composed of stainless steel. The DCF-1-120 flush-mounted flashing lights have a net weight of 50 kg, with the outer ring of the housing upper part weight of 18 kg. The diameter of the outer ring is 559 mm, the overall height 464 mm, while the projection of the housing upper part above ground level is 25.4 mm.
The loads which occur as a result of normal modern aircraft types landing on them, rolling over them or static loads should cause damage neither to the flush-mounted flashing light itself nor to aircraft undercarriages. One critical variable in this case is the projection of the housing cover above ground level. On the other hand, it is advantageous for simple and low-cost installation and maintenance for the flush-mounted flashing light to be as compact as possible and to be light in weight.